Herald and tribune. [volume] (Jonesborough, Tenn.) 1869-current, 1887-01-20
A PLAUSIBLE THEORY.
seeds Carried Thousands of Miles by Strong
Atmnsnhr erin Curranfa.

SEEDS Carried Thousands Of Miles by Strong
atmospheric Currents.
At the meeting of the National Acad-
envy of Scientists Prof. Alfred Russell
Wallace, the visiting English natur-
alist, read the most generally popular
paper which was presented, the subiecI
being: "The Wind as a Seed Carrier il
Relation TO One of the Difficult Prob.
lens in Geographical Distribution. :"
A problem which has greatly interested
botanists is that some species of plants
which have wide distribution in tn
southern hemisphere are also common
plants IN the north, many of them BE-
ing of the Arctic flora, said the speaker.
This fact was considered as remarkable
by Sir Joseph Hooker and has beel
so considered by other naturalists. Tn,
number OF plants so distributed is con
siderable, there being from fifty to sixt
species i'll New Zealand and about th,
same number each in Australia an,
Patagonia, all of which are identified
with those of northern ATTITUDES, man,
being common British plants. Darwin
proposed as the cause the temperature
due to the extension of the glaciers to
the equator, but this theory is now
found to disagree with known facts
Five causes Of distribution of seeds are
prominent: One, sea currents; two.
birds eating fruits, the seeds of which
after digestion are found TO be widely
distributed; three, seeds of marsh
plants, being in the mud which adheres
to the feet Of wading birds, are carried
long distances; four, sticky seeds which
attach themselves to the feathers of
birds, and, fifth, the agency of
the wind. Another fact which must
be taken in connection with the, fifth
cause Is that seeds must needs find
comparatively bare areas of earth in
which to gcrminate. In England, on
the bare earth of railway cuts, the
ilora which Grew afterward was found
to be alwayy different from that of the
adjacent coatry; so on high mount
aims and bare areas over the earth are
The fields for introduced flowers. While
the power OF the wind to transport
seeds is not yet determined, still the
weight of evidence is that it is ample
;or the tr9n pOrtation of small, light
3eeds through considerable distance.
Dust particles from the Java eruption,
of greater weight than many seeds,
were found on the decks of vessels at
from nine hundred to one thousand
miles distance at sea. Taken in con-
neetion will the fact that these intro
duced plants are mostly light-seeded
mes, the wind, without question, is q
most important factor in their distribu-
lion. Prof. Wallace estimated that II
a single seed per square mile of terri
tory were deposited once per hundred
years It would be sufficient to keep up
the stock and to maintain tho purity
of the species. In his book on the
Azores he had called attention to the
fact that neither ocean currents nor
birds would dxplaii. the occurrence OF
certain European plants there, which
can only be explained as having been
wind-borne. 1t is not even the usual
atmospheric currents which transport
the seeds, since prevailing winds as
well as ocean currents are from the
west, but it is the occasional tenn
pestuous outbursts Of atmospheric
energy. A corroborative proof Of the
! efficacy of the winds in distribution is
found in the fact that the species found
on mountains in lower latitudes are
| mostly Arctic for the reason that seeds
from the temperate zone when blown
up to high attitudes would fail to ger
inmate. Boston Globe. -.